"The weather conditions were not good out there. There is a lot of thick cloud and rain around," Mr Regan said.

"The fuel would have expired around the time we lost communications with the aircraft, so it is not looking good."

The aircraft was manufactured in 1934 in the United Kingdom and first registered in Australia in 1936.

Des Porter with the restored bi-plane which was used in the 1930s by the Royal Flying Doctor Service, it is one of only four in the world. Photo: Nicola Brander / Caboolture News.Nicola Brander

A collector's item, the plane carried the call sign VH-UXG and was one of the oldest still registered in the country.

Mr Porter was an experienced pilot with more 20 years flying knowledge. He survived a fatal crash in the same model aircraft when he was a 10-year-old.

His father - who was flying that aircraft - and his older brother were killed when it went down in a creek in Brisbane's south.

Mr Regan said Mr Porter had been flying blind in thick cloud for almost two hours when his plane ran out of fuel.

"Normally he would be flying visually, so he would be flying below the cloud line, but unfortunately he found himself in cloud," he said.

"His first inkling as a pilot would have been to try to get out of it, and if you can't get out of it quickly, you need to climb and try not to hit anything."

Emergency workers will scale the rugged hinterland for the aircraft this morning.

A plane fitted with heat-sensing and night-vision technology joined the search last night.Helicopters will resume their search today at first light.

Mr Regan said there were hopes Mr Porter and his passengers were alive.

AGL Action Rescue Helicopter join in the search for a plane missing with six passengers on board.AGL Action Rescue Helicopter

"We are hoping they broke free of the cloud and were able to make a controlled landing somewhere," he said.

"We understand he was an experienced pilot and if was able to find a clear spot, there is still a chance."

Anyone who has seen the aircraft should contact police.

Police said in a statement late Monday night that a search of the areas surrounding Imbil would continue at first light.

Grave fears held for missing pilot and crew

Grave fears are now held for Mr Porter and his five passengers.

A massive air and land search, involving two AGL Action Rescue Helicopters, was launched west of the Sunshine Coast for the red 1934 De Havilland DH84 Dragon.

Queensland Police Service and the Australian Rescue Co-ordination Centre are coordinating a search west of the Imbil area after the plane distress beacon was activated about 2.45pm.

The beacon is no longer active.

FRONT MAN: Des Porter will fly his Dragon in the front of the Barnstormers Over Brisbane on August 20. Photo Vicki Wood / Caboolture NewsVicki Wood

Reports suggest the plane lost visibility somewhere over the northern end of the Sunshine Coast and that it was running low on fuel.

The plane was returning to its base at Caboolture following a weekend airshow in Monto.

Two AGL Action Rescue Helicopters, one from the Coast and the other from Bundaberg, had been tasked to search for the plane until last light.

A spokeswoman for the Action Rescue Helicopter in a release sent at 4.40pm said it had been "some time" since there was any communication from the pilot and that the distress beacon was no longer active.

Anyone who has seen the aircraft or has information about its location are urged to contact local police.